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The practical side of considering loops as waves: Teaching and Self Improvement

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Paul Arden
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Re: The practical side of considering loops as waves: Teaching and Self Improvement

#61

Post by Paul Arden » Sat Oct 17, 2020 4:50 pm

Incidentally I don’t collapse casts this way, I either use trajectory to collide the leader with the water or under-power wide loops.

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James9118
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Re: The practical side of considering loops as waves: Teaching and Self Improvement

#62

Post by James9118 » Sat Oct 17, 2020 4:51 pm

Hi Paul,

I think in your zero wind scenario you are in the situation that I've described as needing an input from the rod leg in order to complete the cast. I suspect this is because the losses are higher in this scenario than the tailing wind one due to drag.

James

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Re: The practical side of considering loops as waves: Teaching and Self Improvement

#63

Post by Paul Arden » Sat Oct 17, 2020 5:59 pm

Hi James,

Was the untethered shooting head experiment delivered with a tail wind?

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Re: The practical side of considering loops as waves: Teaching and Self Improvement

#64

Post by James9118 » Sat Oct 17, 2020 6:24 pm

Hi Paul,

Yes. I don't know about Lasse's test though.

James

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Re: The practical side of considering loops as waves: Teaching and Self Improvement

#65

Post by Lasse Karlsson » Sat Oct 17, 2020 6:43 pm

Both with a tail wind, and some done without wind. And the ones on vimeo with MPR shootinghead is into the wind and with a sidewind.

Just thinking about Graeme's claims. instead of throwing the rod forawrd and taking a couple of steps, it's much easier to just use a shootinghead, and thin mono shootingline, and let go, tension should drop even more that way.

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Re: The practical side of considering loops as waves: Teaching and Self Improvement

#66

Post by Lasse Karlsson » Sat Oct 17, 2020 6:45 pm

No wind, tracking error and too high trajectory....

Need to redo without those faults ;)

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Re: The practical side of considering loops as waves: Teaching and Self Improvement

#67

Post by Torsten » Sat Oct 17, 2020 6:55 pm

Graeme:
Thanks for the constructive input Torsten
You're welcome :)
To elaborate a little bit more, the wave stuff does not convince me, because I don't consider the loop as a (typical) wave.
Maybe it makes sense in some cases like mends, snake cast or of you see some kind of "wavey" shape in the loop to talk about waves - anything else would be rather misleading and confusing (at least for me).

In general I don't think that you need to know much about physics if you want to learn fly casting. I think useful are guidelines or some basic principles like the 5 Essentials. OK, physics is helpful to debunk wrong explainations.

Take for instance "loop morphing":
How does a loop morph?

The two factors controlling a wave are tension and linear mass. When we increase tension in the rod leg, we increase the speed of the wave through the line. That compresses the wave in the rod leg and at the nose of the loop, but less so in the fly leg, so the loop changes shape and gets tighter (in this scenario).

When we change the linear mass of the line we also change the shape of the loop. The long rear taper of a MED line will produce a change in the loop shape as the wave progresses through it.
Do I really need to know anything about loop morphing to learn fly casting? Yes, it's an interesting phenomen, but IMHO I need only to understand how to cast/control a narrow or a wide loop.

The above text also does not explain the asymmetric loop shape that you're getting often when the loop morphs. In my opinion is loop morphing just a result of forces acting on the loop when it unrolls - such as the drag forces or the force that's a result of the change of momentum at the loop front. Interesting for geeks like me but rather not for the (fly casting) learner.
If there is no tension in the rod leg in these distance events, why is the rod leg not falling at the same rate we'd expect all objects on earth to fall at?
Like above, forces acting against the gravity force such as drag force, change of momentum at the loop front etc.

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Re: The practical side of considering loops as waves: Teaching and Self Improvement

#68

Post by Graeme H » Sun Oct 18, 2020 12:41 am

Thanks for taking a little bit more time Torsten.
Torsten wrote:
Sat Oct 17, 2020 6:55 pm
If there is no tension in the rod leg in these distance events, why is the rod leg not falling at the same rate we'd expect all objects on earth to fall at?
Like above, forces acting against the gravity force such as drag force, change of momentum at the loop front etc.

(Once again, knowing that I am answering in the wrong forum because this one is about teaching ....)

Interesting answer. What is the force causing the change of momentum at the loop front?

Cheers,
Graeme
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Re: The practical side of considering loops as waves: Teaching and Self Improvement

#69

Post by Graeme H » Sun Oct 18, 2020 3:35 am

Paul Arden wrote:
Sat Oct 17, 2020 4:43 pm
I was making short casts today and trying to get the loop to just unroll and then pushing through as Graeme suggests. The loop does indeed form slack on roll out. Whether I’ve changed anything prior to this during the stroke I can’t say 100% but I certainly tried not to - in fact I was trying to prove Graeme wrong :p However when line speed was initially higher and I pushed the loop still unrolled straight (so he is half wrong!).

Cheers, Paul
I'm very glad you gave this a try Paul. I'm also glad you added a bit of extra speed and found the loop didn't collapse. I'm pleased James, Lasse and I are not the only people here doing experiments.

If you recall the original conditions (see below) I did state that the cast is made with JUST enough line speed to unroll. When you added additional line speed, you added extra tension from the fly leg to the loop and made it much more difficult to remove all tension from the rod leg. The loop does not collapse under those conditions, as we'd predict from the physics concept of a wave propagating through a string under tension.

To make the cast collapse with the extra line speed, I would expect that you would need to be moving the tip forward faster than that line speed. The higher the line speed, the harder it is to throw the tip forward with enough speed and displacement to introduce significant slack into the rod leg before the fly leg reestablished tension in the rod leg.

Cheers,
Graeme
In post #19, I wrote:Where this really shows itself to behave as a transverse wave (to me) is when the cast is made with an absolute minimum amount of power, reducing the line speed to just enough to complete the cast. At this extreme of casting power, it's easier to see how tension impacts upon the loop propagation and how tension can be used to both improve my own cast and teach others how they can improve theirs.

Here, we can add tension with the rod tip and complete a beautiful, effortless cast, or we can throw the rod forward and prevent the loop reaching the leader. If we also rapidly run forward (in the park, not on the water! :) ) we can actually make the loop completely collapse in an unrecoverable fashion. The fly leg carries on for a bit before "giving up" and crashing into itself like a mess of wet spaghetti. The loop (wave) disappears and the whole line falls to the ground. In other words, remove the tension from the string and a wave can't propagate.
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Graeme H
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Re: The practical side of considering loops as waves: Teaching and Self Improvement

#70

Post by Graeme H » Sun Oct 18, 2020 4:29 am

James9118 wrote:
Sat Oct 17, 2020 4:01 pm
What makes you think it isn't (falling at 1g)?
Observation, experimentation, etc.


James9118 wrote:
Sat Oct 17, 2020 4:01 pm
Why do you think mine and Lasse's non-tethered casts went further than the tethered ones?
I'm talking about a wave propagating through a medium. Can you remember what that loop looked like, rather than how far it went when you were aiming for maximum distance?

But to answer your question, I think the non-tethered ones went further because they weren't tethered. There is friction of the line on the guides when it's tethered. That was the reason you did the experiment.
James9118 wrote:
Sat Oct 17, 2020 4:01 pm
I look forward to your video - thanks.
Here ya go:



Collapse_1_screen.png
The rod tip was travelling at a maximum calculated* velocity of between 13 and 14 m/s for all four casts. The loop loses its shape on the final cast when the slack is introduced to the rod leg. That slack remains throughout the rest of the cast, as evidenced by the line hanging from the rod tip as I walk forward.

Also, check out what the dolphin nose does when it's allowed to overtake the loop nose ...

Cheers,
Graeme

* I say "calculated" because I'm not sure if the frame rate was correct. In any case, it's consistent.
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